Wednesday, April 6, 2011

Energy Drinks: No Effect on Repeated Sprints

Energy drinks such as Red Bull are becoming increasingly popular among young athletes. Energy drink companies now sponsor many athletes and sports teams including New York Red Bull of Major League Soccer. Thus, it is not surprising that many high school age players regularly drink one or two servings of an energy drink prior to competition. When asked, they comment that the “caffeine shot” improves their strength, alertness, quickness and endurance. However, is this truly the case? Do energy drinks actually improve performance during a soccer match? A study just released in the journal Amino Acids examined the effect of drinking one can of Red Bull prior to exercise. The investigators found that a single serving of the energy drink does not improve repeated sprint performance.

The study, conducted at California State University, San Marcos enrolled 15 players from the women’s varsity soccer team. At the time of the study, the team was in their competitive season and trained for about 12 hours per week.

One hour prior to the exercise test, they were asked to drink either one serving of Red Bull (255 ml or 8.4 oz) or a placebo drink. They returned for a second day of testing and the drinks were reversed. The Red Bull drink contained 80mg of caffeine, 1 g of taurine and 27 g of carbohydrate.

The exercise testing required subjects to complete 24 “all out” sprints over the length of the soccer field. The sprints were separated into 3 sets with 30 seconds rest allowed between sprints and 5 min between sets. Given this, it probably took about 25 minutes to complete all 24 sprints. For each sprint, finish time was recorded as well as heart rate and ratings of perceived exertion (RPE, a measure of perceived effort).

Finish times varied across the 24 sprints. However, there was no difference between conditions. Average finish time for the Red bull condition was 11.31 sec compared to 11.35 sec for the placebo trials. As for individual results, 5 players showed some improvement with Red Bull, 5 showed decreased performance and 5 showed no difference between conditions.

Likewise, heart rates and RPE values varied across the trials but there were no differences between conditions.

Overall, the results of this study showed that one serving of Red Bull, taken one hour prior to exercise, had no effect on repeated sprint performance. In addition, the energy drink did not affect the subjects’ perceived effort. That is, the subjects did not “feel” any better when sprinting after Red Bull drink.

The research on the effects of energy drinks on exercise performance is quite variable. A few studies show that they improve time to exhaustion during prolonged exercise while others show no effect at all. Another study indicates that performance on agility tests is not affected by energy drinks. Part of the difference in results between studies may be the amount of drink consumed and the caffeine content. In this study, 80 mg of caffeine was given while in other studies provided up to four times that amount. Would two cans of Red Bull have improved performance? Perhaps, but 80 mg of caffeine in a single serving of Red Bull improves variables such as alertness. Also, similar amounts of caffeine can spare muscle glycogen which might improve endurance performance. However, more caffeine can cause unwanted side-effects such as nausea, feelings of anxiety and the need to urinate. In fact, two subjects in this study reported the first two of effects. Obviously, either of the three could hinder performance. So, it is not clear if 2-3 cans of Red Bull would have changed the results.

Interpreting research on caffeine and energy drinks can be difficult. As pointed out above, the amount of caffeine consumed varies from one study to the next. Second, individual subjects’ tolerance to caffeine might affect how they respond to an energy drink. For example, habitual coffee drinkers have a greater tolerance to caffeine than do no-coffee drinkers. Third, researchers often examine the effects of caffeine on different types of exercises ranging from prolonged exercise to strength and speed to agility. Thus, it is not surprising that some studies find benefits and others do not. It is also not surprising that one athlete may feel that an energy drink greatly improves his or her performance during a match while another feels no effect at all.

In the end, this study suggests that drinking a 255ml (8.4 oz) can of Red Bull prior to a soccer match is unlikely to have any effect on sprint performance or how one feels during the match. Taking a more solid approach to pre-match nutrition that includes a high carbohydrate meal, drinks and snacks will likely lead to better results that resorting to a quick-fix energy drink. As for young athletes, the vast majority of experts recommend against using energy drinks as way to improve performance. The potential for unwanted short-term and long-term side-effects clearly outweigh any possible performance benefits.

Reference:

Astorino TA, Matera AJ, Basinger J, Evans M, SchurmanT, Marquez R (2011) Effects of red bull energy drink on repeated sprint performance. Amino Acids, DOI: 10.1007/s00726-011-0900-8